Adaptive low-complexity channel estimation

ABSTRACT

Systems, methods, and other embodiments associated with adaptive low-complexity channel estimation are illustrated. In one embodiment an integrated circuit includes a controller configured to control a switch to select between a plurality of processing paths that each perform channel estimation using a different order of operations to process an orthogonal frequency-division multiplexed (OFDM) signal.

CROSS REFERENCE TO RELATED APPLICATIONS

The patent disclosure is a continuation of U.S. patent application Ser.No. 13/282,952 filed Oct. 27, 2011, now U.S. Pat. No. 8,699,644, whichclaims benefit under 35 USC §119(e) to U.S. Provisional Application No.61/407,692 filed on Oct. 28, 2010, which are both hereby incorporated byreference in its entirety.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventor(s), to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Orthogonal frequency-division multiplexing (OFDM) is a signal modulationtechnique often used with wireless communications and some wiredcommunications. OFDM offers high transmission rates and, thus, isbeneficial for use in data networks. However, several difficulties maybe encountered when attempting to efficiently process OFDM signals in areceiver. For example, processing an OFDM signal according to atwo-dimensional technique, while efficient is overly complex for mostimplementations. Thus, a trade off for a less complex processingsolution may be implemented. In one example, this may includeone-dimensional processing techniques. However, one-dimensionalprocessing can suffer from processing inefficiencies. Processinginefficiencies for a one-dimensional technique arise when conditionsassociated with an OFDM signal fall outside of an operational range foran implemented solution. Thus as conditions of the OFDM signal change,processing efficiency can be significantly reduced.

For example, consider a wireless network interface card (NIC) that usesa low complexity solution to process an OFDM signal received from awireless access point. Typically, the low complexity solution is tunedto perform well for a specific set of operating conditions (e.g., slowlychanging frequency selectivity). Thus, when the operating conditionsfall outside of the tuned operation conditions (e.g., quickly changingfrequency selectivity), processing becomes inefficient and systemperformance suffers.

SUMMARY

In one embodiment, a device includes a controller configured to controla switch to select between at least two processing paths when performingchannel estimation processing of an orthogonal frequency-divisionmultiplexed (OFDM) signal. The at least two processing paths include afirst processing path configured to process the OFDM signal according toa first order of processing operations, and a second processing pathconfigured to process the OFDM signal according to a second order ofprocessing operations. The first order of processing operations isdifferent from the second order of processing operations.

In another embodiment, a method includes receiving an orthogonalfrequency-division multiplexed (OFDM) signal in a communication device.The method includes controlling the communication device to selectbetween at least two processing paths for performing channel estimationprocessing of the OFDM signal. Controlling the communication device toselect between the at least two processing paths includes controllingthe communication device to select between two separate orders forperforming processing operations on the OFDM signal.

In another embodiment, an integrated circuit includes a controllerconfigured to control a switch to select between a plurality ofprocessing paths that each perform channel estimation using a differentorder of operations to process an orthogonal frequency-divisionmultiplexed (OFDM) signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate various systems, methods, andother embodiments of the disclosure. Illustrated element boundaries(e.g., boxes, groups of boxes, or other shapes) in the figures representone example of the boundaries. In some embodiments, one element may bedesigned as multiple elements or that multiple elements may be designedas one element. In some examples, an element shown as an internalcomponent of another element may be implemented as an external componentand vice versa. Furthermore, elements may not be drawn to scale.

FIG. 1 illustrates one embodiment of a device associated with adaptivelow-complexity channel estimation.

FIG. 2 illustrates one embodiment of a method associated with adaptivelow-complexity channel estimation.

FIG. 3 illustrates one example of a transmission frame of an OFDM signalat two different points during processing.

FIG. 4 illustrates one example of a received OFDM signal at twodifferent points in time.

FIG. 5 illustrates one embodiment of a method for determining whichprocessing path to select for processing the OFDM signal.

FIG. 6 illustrates one embodiment of an integrated circuit associatedwith switching processing paths when performing adaptive low-complexitychannel estimation.

DETAILED DESCRIPTION

Described herein are systems, methods, and other embodiments associatedwith adaptive, low-complexity channel estimation for processing anorthogonal frequency-division multiplexing (OFDM) signal. In oneembodiment, a communications device adaptively switches betweendifferent processing circuits depending on dynamic conditions of theOFDM signal. In this way, processing efficiency for the OFDM signal maybe maintained as channel conditions for the OFDM signal change.

FIG. 1 illustrates one embodiment of a device 100 associated withadaptive, low-complexity channel estimation. The device 100 includes areceiver 110, a measurement logic 120, a switch controller 130, and aswitch 140. The device 100 may also include a first processing path 150,a second processing path 160, and a pilot demodulation logic 170. In theembodiment shown in FIG. 1, the first processing path 150 is configuredto first perform frequency-domain processing followed by time-domainprocessing, and the second processing path 160 is configured to firstperform time-domain processing followed by frequency-domain processing.

FIG. 1 will be discussed in greater detail in conjunction with FIG. 2.FIG. 2 illustrates one embodiment of a method 200 associated withadaptive, low-complexity channel estimation. FIG. 2 is discussed fromthe perspective that the method 200 is implemented and performed by thedevice 100 to adaptively control the switch 140 to select a processingpath—e.g., the first processing path 150 or the second processing path160—based, at least in part, on channel conditions for an OFDM signal.

At 210, the receiver 110 receives an orthogonal frequency-divisionmultiplexed (OFDM) signal. In one example, the OFDM signal is a wirelesscommunication sent from a transmitting device to the device 100. Thedevice 100 can be, for example, a wireless communications device that iscompatible with IEEE 802.16, 3^(rd) Generation Partnership Project LongTerm Evolution (LTE), IEEE 802.11, and so on. Additionally, the device100 can be, for example, a cellular phone, a smartphone, a handhelddevice, a wireless network interface card (NIC), and so on. Wired mediumcommunication techniques including, for example, Digital Subscriber Line(DSL) technology may also use OFDM transmissions.

In one embodiment, the device 100 is configured to wirelesslycommunicate with other devices by sending and receiving OFDM signals. AnOFDM signal is a data carrier signal that includes multiple frequencysub-carriers. For example, FIG. 3 illustrates a portion or frame of anOFDM signal at two successive points (e.g., frame 310 a and frame 310 b)during processing.

Consider that frame 310 a illustrates multiple frequency sub-carriersalong the y-axis and successive points in time for the sub-carriersalong the x-axis. Thus, frame 310 a illustrates a representative portionof the OFDM signal for fourteen successive points in the time domainwith twelve sub-carriers spaced at regular intervals in the frequencydomain. A block in frame 310 a illustrates an OFDM symbol (e.g., 312).An OFDM symbol is a data point in the OFDM signal.

Additionally, darkened blocks 312, 314, and 316 are examples of OFDMsymbols that are part of a pilot pattern that includes other OFDMsymbols throughout the OFDM signal (represented here by darkenedblocks). The pilot pattern is a set of OFDM symbols known to the device100 prior to receiving the OFDM signal.

One example of processing these signals may be as follows. Atransmitting device places the symbols of the pilot pattern (alsoreferred to herein as “pilot pattern symbols”) into the OFDM signal. Areceiving device (e.g., device 100) is programmed to recognize the pilotpattern and therefore knows the pilot pattern prior to receiving thetransmission (e.g., pilot pattern is pre-determined and stored inmemory). Thus, the values and locations of the pilot pattern symbols areknown to the device 100 prior to the device 100 receiving the OFDMsignal. The demodulation logic 170 (shown in FIG. 1) in the device 100compares the values of the pilot pattern symbols in the received OFDMsignal to known values of the pilot pattern symbols. In this way, thedemodulation logic 170 correlates the pilot pattern in a received OFDMsignal to the known pilot pattern to determine a channel response forthe received OFDM signal. The channel response is, for example, thesignal distorting characteristics of the communication channel thatinfluence the OFDM signal as the OFDM signal propagates through awireless medium from the transmitting device to the device 100.

The device 100 uses the channel response determined from the comparisonof the pilot pattern values when processing the OFDM signal. The device100 performs, for example, channel estimation on the OFDM signal toreconstruct a channel response in the OFDM signal between the pilotpattern symbols (e.g., dark blocks 312, 314, 316). In one embodiment,the channel estimation is performed by successively processing the OFDMsignal in one domain at a time (e.g., frequency domain first and thentime domain second). The processing includes, for example, a filteringprocess and/or interpolation between the pilot pattern estimatesdetermined previously by the demodulation logic 170.

However, depending on channel conditions of the OFDM signal, processingin a static order (e.g., always frequency and then time) can beinefficient. Thus, at 220 in FIG. 2, the measurement logic 120determines channel conditions for the OFDM signal. At 230, the channelconditions are then used to select a processing path (e.g., firstprocessing path 150 or second processing path 160 in FIG. 1) for theOFDM signal. In this way, when the channel conditions change, the device100 can adaptively switch processing paths to maintain efficiency inprocessing the OFDM signal and possibly avoid performance degradation.

With reference to FIG. 1, in one embodiment, the measurement logic 120determines the channel conditions by measuring the channel conditionsfrom the OFDM signal and/or the demodulated pilot symbols (i.e., thechannel responses at the pilot sub-carriers) from 170. This function isperformed at 220 in FIG. 2. The channel conditions are attributes of theOFDM signal. For example, the channel conditions may include a frequencycorrelation, a time correlation, and so on. The frequency correlationis, for example, a difference in values of pilot pattern symbols fromthe OFDM signal in the frequency domain. The time correlation is, forexample, a difference in values of pilot pattern symbols from the OFDMsignal in the time domain.

In one embodiment, the measurement logic 120 uses, for example, symbolsin the OFDM signal that correlate with the pilot pattern to measure thefrequency correlation and the time correlation. For example, themeasurement logic 120 measures the frequency correlation from an amountof change in a value between two pilot pattern symbols in the OFDMsignal in the frequency domain. Thus, by measuring a differentialbetween pilot pattern symbols as received in the OFDM signal, channelconditions of the OFDM signal can be determined that are useful whenselecting a processing path. In this way, the measurement logic 120 candetermine values that are then provided to the controller 130 whichdetermines and selects one of the processing paths 150 or 160.

Consider graph 400 as shown in FIG. 4 where the channel response isillustrated at time=0 (reference line 410) and time=1 millisecond(reference line 420). In this example, both 410 and 420 are samples ofchannel response from the received OFDM signal that include pilotpattern symbols. Let R_(f) represent a frequency correlation and R_(t)represent a time correlation for the OFDM signal. In one embodiment,R_(f) is measured between, for example, pilot pattern blocks 312 and 316of FIG. 3 which correlate to the two points on the line 410 denoted byR_(f) in FIG. 4. The measurement logic 120 measures the value at 312 andthe value at 316 and, for example, determines a difference in the valuesto produce the frequency correlation R_(f). In FIG. 4, the values for312 and 316, for example, are the values given by |H(f)| in the y-axisfor a subcarrier as corresponding to a frequency specified on thex-axis. Thus, R_(f) represents a degree of change in value of the signalbetween 312 and 316 (e.g., change in the frequency domain betweendifferent subcarriers).

In one embodiment, the measurement logic 120 determines the timecorrelation by measuring an amount of change in a value between twopilot pattern symbols in the OFDM signal in the time domain. Forexample, R_(t) may be measured between pilot pattern blocks 312 and 314of FIG. 3 which correlate with the points on the line 410 and the line420 denoted by the vertical arrow line R_(t) in FIG. 4. In oneembodiment, the measurement logic 120 measures the value at 312 and thevalue at 314 and determines a difference in the values to produce thetime correlation R_(t). Thus, R_(t) represents a degree of change in thetime domain for the OFDM signal between 312 and 314 (e.g., change in thetime domain between the same subcarriers).

In one embodiment, the frequency and time correlation are measured bythe measurement logic 120 based on the received signal and thetransmitted pilot symbols.{circumflex over (R)}^_(f)(k)=G(y _(ij)(t),s _(i) _(p) _(j) _(p) (t)), R_(t)(m)=H(y _(ij)(t),s _(i) _(p) _(j) _(p) (t))

Where G( ) and H( ) are the functions of the frequency and timecorrelation measurement.

One example of how the measurement logic 120 may determine R_(f) andR_(t) is given by:

${{R_{f}(k)} = {\frac{1}{N_{f}}{\sum\limits_{i_{p},j_{p}}\frac{\left( {y_{i_{p}j_{p}}s_{i_{p}j_{p}}^{*}} \right) \times \left( {y_{i_{p}{({j_{p} + {k\;\Delta\; f}})}}s_{i_{p}{({j_{p} + {k\;\Delta\; f}})}}^{*}} \right)^{*}}{{{y_{i_{p}j_{p}}s_{i_{p}j_{p}}^{*}}} \times {{y_{i_{p}{({j_{p} + {k\;\Delta\; f}})}}s_{i_{p}{({j_{p} + {k\;\Delta\; f}})}}^{*}}}}}}};$Δ f:  pilot  freq  spacing${{R_{t}(m)} = {\frac{1}{N_{t}}{\sum\limits_{i_{p},j_{p}}\frac{\left( {y_{i_{p}j_{p}}s_{i_{p}j_{p}}^{*}} \right) \times \left( {y_{{({i_{p} + {m\;\Delta\; t}})}j_{p}}s_{{({i_{p} + {m\;\Delta\; t}})}j_{p}}^{*}} \right)^{*}}{{{y_{i_{p}j_{p}}s_{i_{p}j_{p}}^{*}}} \times {{y_{{({i_{p} + {m\;\Delta\; t}})}j_{p}}s_{{({i_{p} + {m\;\Delta\; t}})}j_{p}}^{*}}}}}}};$Δ t:  pilot  time  spacing

y_(ij) is the received signal at the j^(th) frequency subcarrier in thei^(th) OFDM symbol.

Si_(p)j_(p) is the pilot symbol at the j_(p) ^(th) subcarrier in thei_(p) ^(th) OFDM symbol.

i denotes the correlation measurement time window and j denotes thecorrelation measurement frequency band.

(i_(p),j_(p)) represents the pilot location within the correlationmeasurement region.

m and k represent a distance between two pilot pattern symbols that arecompared to measure the frequency correlation or the time correlation inthe frequency or the time domain, in unit of subcarriers or symbols.

N_(f) is the total number of measurements of frequency correlation inthe measurement band.

N_(t) is the total number of measurements of time correlation in themeasurement window.

The measurement logic 120 may determine R_(f) and R_(t) for a pluralityof points within the signal to provide more data points when decidingwhich processing path to select. Additionally, in one embodiment, themeasurement logic 120 monitors the OFDM signal to iteratively determinethe channel conditions. Thus, the measurement logic 120 maintains, forexample, short term values of R_(t) and R_(f) and/or long term values offor R_(t) and R_(f). In one example, the averages may be maintainedacross transmission frames for the OFDM signal.

In one embodiment, the averaged correlations are represented by:{circumflex over (R)}^_(f)(k;t)=G(y _(ij)(t),s _(i) _(p) _(j) _(p) (t)),R _(t)(m;t)=H(y _(ij)(t),s _(i) _(p) _(j) _(p) (t))R _(f)(k;t)=Q({circumflex over (R)}^_(f)(k;τ);τ=0 . . . t), R_(t)(m;t)=P(R _(t)(m;τ);τ=0 . . . t)

For example, the long term values can be obtained by a one-pole IIRfilter, or a moving average for the frequency correlation as representedby, for example:

${R_{f}\left( {k;\overset{-}{t}} \right)} = {{\left( {1\mspace{14mu}\alpha} \right){\hat{R}}_{f}} + {\left( {k;t} \right)\mspace{11mu}\alpha\; R_{f}} - \left( {k;{t\; 1}} \right)}$${R_{f}\left( {k;t} \right)} = {\frac{1}{L}{\sum\limits_{l = 0}^{L - 1}{{\hat{R}}_{f}\left( {k;{t - l}} \right)}}}$

α represents the forgetting factor of the one-pole IIR filter, and L isthe size of the moving average window.

In one embodiment, the determined channel conditions are provided by themeasurement logic 120 to the controller 130. While R_(f) and R_(t) arediscussed, it should be appreciated that other channel conditions forthe OFDM signal may be measured and provided to the controller 130 foruse in determining which processing path to select.

With reference again to FIG. 1, in one embodiment, the controller 130 isimplemented with one or more logic components as defined herein and isstructure configured to perform the functions described herein. Forexample, the controller 130 determines which processing path to use andcontrols the switch 140 to select between the first processing path 150or the second processing path 160. The controller 130 uses, for example,the channel conditions from the measurement logic 120 to determine whichprocessing path (e.g., 150 or 160) to select. For example, consider thechannel conditions from FIG. 4. The frequency correlation is high since312 and 316 are close in value as illustrated in FIG. 4 (e.g., 2.4−2.4=0where H(f) represents a value of an associated subcarrier). Thus,processing in the frequency domain first is an efficient choice sincethe change in the frequency domain is low. However, selecting the timedomain first for processing in this example would not be an efficientchoice since the time correlation value between 312 and 314 is large incomparison to the frequency correlation (e.g., 2.4−1=1.4). Therefore,selecting the time domain first would likely result in performancedegradation.

Accordingly, at 230 in FIG. 2, with the channel conditions determined,method 200 selects the first processing path 150 and proceeds to 240where the first processing path 150 first processes the OFDM signal inthe frequency domain and then, at 250, the method processes the signalin the time domain. Method 200 then returns to 210 where a new frame forthe OFDM signal is received for processing and the method continues.

One example of processing the signal via the first processing path 150is illustrated in FIG. 3. For example, frame 310 a illustratesprocessing of a transmission frame of the OFDM signal in the frequencydomain. To perform one-dimensional frequency domain processing, thefirst processing path 150, for example, interpolates values for OFDMsymbols in columns (e.g., y-axis) with pilot pattern symbols asillustrated by the arrows. In this way, values between the known pilotpattern symbols are determined.

After performing the frequency domain processing, logic in the firstprocessing path 150 performs time domain processing on the partiallyinterpolated frame 310 b. Logic in the first processing path 150 isconfigured to interpolate symbols in the frame 310 b in the time domain(x-axis) between the values previously interpolated during frequencydomain processing. Subsequent frames from the OFDM signal are processedsimilarly.

Alternatively, if the channel conditions indicate a low frequencycorrelation relative to the time correlation, the controller 130controls the switch 140 to select the second processing path 160. Thus,the OFDM signal is processed with logic configured to perform timedomain processing first and then perform frequency domain processingsecond. The second processing path 160 performs time domain processingby, for example, interpolating symbols in rows (e.g., x-axis) with pilotpattern symbols. After performing the time domain processing, the secondprocessing path 160 performs frequency domain processing on thepartially interpolated frame. In this example, the second processingpath 160 interpolates symbols in the frame in the frequency domain(y-axis) between the values previously interpolated during time-domainprocessing. This processing scenario is represented by FIG. 2 atdecision 230, where the process proceeds to time domain processing at260 and then frequency domain processing at 270.

In another embodiment, instead of selecting between processing paths at230, method 200 includes, for example, performing multipledeterminations to determine which processing path to select. Forexample, with reference to FIG. 5, one embodiment of block 230 of method200 is illustrated that includes decision blocks 510 and 520. In thisexample, at 510, the method determines whether the frequency correlationfrom the measurement logic 120 is within a predetermined frequencythreshold. If the frequency correlation R_(f) for the OFDM signal is,for example, larger than the predetermined frequency threshold then theOFDM signal is processed by the first processing path 150 as indicatedat 240.

However, if the frequency correlation R_(f) is not within (i.e., largerthan) the predetermined frequency threshold, then the method proceeds to520. At 520, the method determines whether the time correlation R_(t)for the OFDM signal is within a predetermined time threshold. If thetime correlation R_(t) is within the predetermined time threshold, thesecond processing path 160 is selected and the method proceeds to 260where the signal is processed in the time domain first. However, if thetime correlation R_(t) is not within the predetermined time threshold,then the first processing path 150 is selected and the method proceedsto 240 where the signal is processed in the frequency domain first. Inone embodiment, the controller 130 of FIG. 1 is configured to performthe actions at 510 and 520 of FIG. 5.

Furthermore, instead of defaulting to the first processing path 150after 520, in one embodiment, method 200 continues by using channelconditions measured between pilot pattern symbols spaced further apartwith a second set of thresholds to determine a processing path. Forexample, instead of calculating R_(f) between 312 and 316, R_(f) may becalculated between 312 and a pilot pattern symbol that is an additionalinterval away (e.g., an additional 6 blocks in frequency from 316).Thus, measurement logic 120 measures a second frequency correlationR_(f2) at 220 in FIG. 2 between pilot pattern symbols that are, forexample, 12 blocks apart. Thus, if the determination at 520 in FIG. 5 isno, then method 200 proceeds to determine whether the second frequencycorrelation R_(f2) is within a second predetermined frequency threshold.If the second frequency correlation R_(f2) is within the secondpredetermined frequency threshold, then method 200 proceeds to 240.

If the second frequency correlation R_(f2) is not within the secondpredetermined frequency threshold, then method 200 proceeds to determinewhether a second time correlation R_(t2) (also determined at 220) iswithin a second predetermined time correlation threshold. If the secondtime correlation R_(t2) is within the second predetermined timethreshold, then method 200 proceeds to 260, otherwise method 200defaults to 240. In this way, method 200 may avoid defaulting to thefirst processing path 150 and proceed to 240 when an additionaldetermination may prevent performance degradation by facilitatingselection of a better path. In other embodiments more iterations ofblocks 510 and 520 may be performed to facilitate improving theselection of a processing path.

With reference to FIG. 6, one embodiment of an integrated circuit 600associated with switching processing paths when performing adaptivelow-complexity channel estimation is illustrated. FIG. 6 illustrates anembodiment of the integrated circuit 600 that includes the measurementlogic 120, the controller 130, and the switch 140 of FIG. 1. Theintegrated circuit 600, for example, connects to the receiver 110, thefirst processing path 150, and the second processing path 160 that areincluded on circuits separate from the integrated circuit 600. In oneexample, the processing paths 150 and 160 are separate circuitsconfigured to perform the successive one-dimensional processing of theOFDM signal in different orders. The processing paths 150, 160 are, forexample, logics for performing successive one-dimensional processing ofthe OFDM signal. Thus, in one embodiment, the integrated circuit 600 maycontrol a path taken by an OFDM signal from the receiver 110 todifferent downstream circuits via first processing path 150 or secondprocessing path 160.

The following includes definitions of selected terms employed herein.The definitions include various examples and/or forms of components thatfall within the scope of a term and that may be used for implementation.The examples are not intended to be limiting. Both singular and pluralforms of terms may be within the definitions.

References to “one embodiment”, “an embodiment”, “one example”, “anexample”, and so on, indicate that the embodiment(s) or example(s) sodescribed may include a particular feature, structure, characteristic,property, element, or limitation, but that not every embodiment orexample necessarily includes that particular feature, structure,characteristic, property, element or limitation. Furthermore, repeateduse of the phrase “in one embodiment” does not necessarily refer to thesame embodiment, though it may.

“Logic”, as used herein, includes but is not limited to hardware,firmware, instructions stored on a non-transitory medium or in executionon a machine, and/or combinations of each to perform a function(s) or anaction(s), and/or to cause a function or action from another logic,method, and/or system. Logic may include a software controlledmicroprocessor, a discrete logic (e.g., ASIC), an analog circuit, adigital circuit, a programmed logic device, a memory device containinginstructions, and so on. Logic may include one or more gates,combinations of gates, or other circuit components. Where multiplelogics are described, it may be possible to incorporate the multiplelogics into one physical logic. Similarly, where a single logic isdescribed, it may be possible to distribute that single logic betweenmultiple physical logics. One or more of the components and functionsdescribed herein may be implemented using one or more of the logicelements. Logic as defined herein is limited to statutory subject matterthat satisfies 35 U.S.C. §101 requirements.

While for purposes of simplicity of explanation, illustratedmethodologies are shown and described as a series of blocks. Themethodologies are not limited by the order of the blocks as some blockscan occur in different orders and/or concurrently with other blocks fromthat shown and described. Moreover, less than all the illustrated blocksmay be used to implement an example methodology. Blocks may be combinedor separated into multiple components. Furthermore, additional and/oralternative methodologies can employ additional, not illustrated blocks.The methods described and claimed herein are limited to statutorysubject matter that satisfies 35 U.S.C. §101 requirements.

To the extent that the term “includes” or “including” is employed in thedetailed description or the claims, it is intended to be inclusive in amanner similar to the term “comprising” as that term is interpreted whenemployed as a transitional word in a claim.

While example systems, methods, and so on have been illustrated bydescribing examples, and while the examples have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe systems, methods, and so on described herein. Therefore, thedisclosure is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Thus, thisapplication is intended to embrace alterations, modifications, andvariations that fall within the scope of the appended claims.

What is claimed is:
 1. A device comprising: a controller configured tocontrol a switch to select between at least two processing paths whenperforming channel estimation processing of an orthogonalfrequency-division multiplexed (OFDM) signal, wherein the at least twoprocessing paths include: a first processing path configured to processthe OFDM signal according to a first order of processing operations; anda second processing path configured to process the OFDM signal accordingto a second order of processing operations, wherein the first order ofprocessing operations is different from the second order of processingoperations; wherein the controller is further configured to: select thefirst processing path if a frequency correlation for the OFDM signal iswithin a predetermined frequency threshold; and select the secondprocessing path if i) a time correlation for the OFDM signal is within apredetermined time threshold, and ii) the frequency correlation is notwithin the predetermined frequency threshold.
 2. The device of claim 1,further comprising: a receiver configured to receive the OFDM signal;and a measurement logic configured to determine channel conditionsassociated with the OFDM signal by using a pilot pattern from the OFDMsignal, wherein the measurement logic is further configured to monitorthe OFDM signal to iteratively determine the channel conditions of theOFDM signal.
 3. The device of claim 1, wherein the controller isconfigured to select between the two processing paths according tochannel conditions associated with the OFDM signal.
 4. The device ofclaim 1, wherein the first processing path includes logic for firstperforming one-dimensional frequency domain processing and thensubsequently performing one-dimensional time domain processing of theOFDM signal; the second processing path includes logic for firstperforming one-dimensional time domain processing and then subsequentlyperforming one-dimensional frequency domain processing of the OFDMsignal, wherein each of the first processing path and the secondprocessing path is configured to perform channel estimation processingon the OFDM signal.
 5. The device of claim 1, wherein the device is awireless communications device that is compatible with IEEE 802.16,WiMAX, LTE, or IEEE 802.11 or a wired communications device that iscompatible with Digital Subscriber Line (DSL) and wherein the device isa smartphone, a handheld device, a DSL modem, or a wireless networkinterface card.
 6. The device of claim 3, wherein the channel conditionsinclude at least the frequency correlation and the time correlation forthe OFDM signal.
 7. A method comprising: receiving an orthogonalfrequency-division multiplexed (OFDM) signal in a communication device;and controlling the communication device to select between at least twoprocessing paths for performing channel estimation processing of theOFDM signal, wherein controlling the communication device to selectbetween the at least two processing paths includes controlling thecommunication device to select between two separate orders forperforming processing operations on the OFDM signal; wherein controllingthe communication device to select between the two processing pathsincludes: selecting a first processing path if a frequency correlationfor the OFDM signal is within a predetermined frequency threshold; andselecting a second processing path if i) a time correlation for the OFDMsignal is within a predetermined time threshold, and ii) the frequencycorrelation is not within the predetermined frequency threshold, whereinthe frequency correlation and the time correlation are channelconditions of the OFDM signal.
 8. The method of claim 7, furthercomprising: determining the channel conditions from the OFDM signalusing a pilot pattern from the OFDM signal.
 9. The method of claim 7,further comprising: monitoring the OFDM signal to iteratively determinethe channel conditions of the OFDM signal, wherein controlling thecommunication device to select between the two processing paths isbased, at least in part, on the channel conditions.
 10. The method ofclaim 7, wherein controlling the communication device to select betweenthe two processing paths includes selecting between: a first processingpath to process the OFDM signal first in the frequency domain and thensubsequently process the OFDM signal in the time domain, and a secondprocessing path to process the OFDM signal first in the time domain andthen subsequently process the OFDM signal in the frequency domain, andwherein the first processing path and the second processing path performchannel estimation processing on the OFDM signal.
 11. The method ofclaim 7, wherein the communication device is compatible with IEEE802.16, WiMAX, LTE, IEEE 802.11, or Digital Subscriber Line (DSL), andwherein the communication device is a smartphone, a handheld device, awireless network interface card, or a DSL modem.
 12. An integratedcircuit comprising: a controller configured to control a switch toselect between a plurality of processing paths that each perform channelestimation using a different order of operations to process anorthogonal frequency-division multiplexed (OFDM) signal, wherein thecontroller is configured to select a first processing path from theplurality of processing paths if a frequency correlation for the OFDMsignal is within a predetermined frequency threshold and to otherwiseselect a different processing path of the plurality of processing paths;and wherein the controller is further configured to: select thedifferent processing path from the plurality of processing paths if i) atime correlation for the OFDM signal is within a predetermined timethreshold, and ii) the frequency correlation is not within thepredetermined frequency threshold.
 13. The integrated circuit of claim12, wherein the plurality of processing paths that each perform channelestimation using a different order of operations includes at least twoprocessing paths that each perform successive one-dimensional processingof the OFDM signal in a different order, and wherein the successiveone-dimensional processing includes processing in a frequency domain andin a time domain.
 14. The integrated circuit of claim 12, furthercomprising: a receiver configured to receive the OFDM signal to beprocessed according to a successive one-dimensional processing path; ameasurement logic configured to determine channel conditions of the OFDMsignal using a pilot pattern from the OFDM signal, wherein the channelconditions include at least the frequency correlation and the timecorrelation for the OFDM signal, wherein the measurement logic isfurther configured to monitor the OFDM signal to iteratively determinethe channel conditions of the OFDM signal as additional frames of theOFDM signal are received.
 15. The integrated circuit of claim 12,wherein the plurality of processing paths selectable by the switchinclude at least: i) a first processing path configured to process theOFDM signal first in a frequency domain and then subsequently processthe OFDM signal in a time domain, and ii) a second processing pathconfigured to process the OFDM signal first in the time domain and thensubsequently process the OFDM signal in the frequency domain, andwherein each of the first processing path and the second processing pathis configured to perform channel estimation processing on the OFDMsignal.
 16. The integrated circuit of claim 12, wherein the integratedcircuit is compatible with IEEE 802.16, WiMAX, LTE, IEEE 802.11, orDigital Subscriber Line (DSL) and wherein the integrated circuit isembedded within a smartphone, a handheld device, a wireless networkinterface card, or a DSL modem.